The present invention relates to bags or packages such as may be formed from plastic film and having an openable mouth with a reclosable extruded plastic fastener or zipper situated inside the mouth. The zipper has complementary profiles that are interlocked when the zipper is closed and can be separated to open the zipper. Bags or packages of this kind are well known and in widespread use.
In the use of plastic bags and packages, particularly for foodstuffs, it is important that the bag be hermetically sealed until the purchaser acquires the bag and its contents, takes them home, and opens the bag or package for the first time. It is then commercially attractive and useful for the consumer that the bag or package be reclosable so that its contents may be protected. Flexible plastic zippers have proven to be excellent for reclosable bags, because they may be manufactured with high-speed equipment and are reliable for repeated reuse.
A typical zipper is one which has a grooved member at one side of the bag mouth and a ribbed member at the other side, which rib may interlock into the groove when the sides of the mouth of the bag are pressed together. Alternatively, a member having a plurality of ribs may be on one side of the bag mouth, while a member having a plurality of channels may be on the other side, the ribs locking into the channels when the sides of the mouth of the bag are pressed together. In such a case, there may be no difference in appearance between the two members, as the ribs may simply be the intervals between channels on a strip that may lock into another of the same kind. In general, and in short, some form of male/female interengagement is used to join the two sides of the bag mouth together. The so-called members, or strips, are bonded in some manner to the material from which the bags themselves are manufactured. Usually, pull flanges extend above the rib and groove strips, which pull flanges may be pulled apart for access to the interior of the bag.
Although flexible zippers of this variety are quite popular, a person attempting to close a reclosable package or bag having opposing ribbed and grooved zipper strips must align the rib with the groove before pressing the rib into the groove. Typically, this is accomplished by pressing the zipper strips together between a thumb and opposing forefinger on one hand while holding one end of the zipper in the other hand. The aligning and pressing procedure must be performed continuously or at multiple discrete intervals along the length of the zipper in order to fully close the mouth of the package or bag. When the reclosable package or bag is made of thin flexible plastic material, it is easy for the plastic fastener strips of the zipper to flex so that the rib and groove are out of alignment in a given area. The larger the size of the package or bag, the greater the amount that the central portions of the fastener strips can misalign. Also, when zipper segment halves are not joined at the segment ends, the user must initiate the closing without any pre-aligned portion of the zipper. Also, although the nature of the construction is such that when the package or bag is empty and flat, the fastener strips are prone to be aligned, misalignment is more likely when the package or bag has been filled and the plastic film of the package or bag has been distended or otherwise shaped by the contents. Consequently, a person may have difficulty closing a reclosable package or bag due to misalignment of the rib and groove fastener strips at one or more points along the length of the zipper.
One parameter which is useful in quantifying the degree to which a plastic zipper is susceptible to misalignment is an aspect ratio formed by dividing the width of the target (i.e., the distance separating apices at the inlet of the female member) by the height of the zipper (i.e., the distance from the back of one fastener strip to the back of the other fastener strip when the male and female members are interlocked). In the prior art zippers known to the inventor, the foregoing aspect ratio is substantially less than unity.
There is a need for a zipper design that makes it easier for a person to cause the interlockable faster strips of a plastic zipper to interlock during closure of reclosable package or bag.
The present invention is directed to a reclosable package or bag having a mouth with an extruded flexible plastic zipper with interlockable male and female members installed in the mouth, the zipper being designed to facilitate alignment of the interlockable male and female members when a consumer tries to close the zipper.
In accordance with one preferred embodiment of the invention, the zipper has an aspect ratio substantially equal to or greater than unity. More specifically, the female member has target apices separated by a distance substantially equal to or greater than the height of the zipper as measured from the bases of the male and female members.
In accordance with another preferred embodiment, the female zipper member comprises opposing resilient walls with outwardly directed extensions or wings at the distal ends of the walls which serve to increase the distance between the target apices, preferably to attain an aspect ratio substantially equal to or greater than unity. These outwardly directed wings guide an off-target or misaligned incoming male zipper member toward the opening in the female member during attempts to close the zipper.
In one example of the second preferred embodiment, the extruded female member comprises a pair of resilient walls having a channel or groove therebetween for receiving the head of the male member, respective inwardly directed extensions (defining an opening therebetween), and respective outwardly directed extensions, both sets of extensions extending from the distal ends of the resilient walls of the female member. Preferably, each wall and its associated inwardly and outwardly directed extensions are integrally formed. Each outwardly directed extension of the female zipper member preferably has an inclined camming surface which is oriented to guide the impinging tip of the incoming male zipper member toward the center plane of the female member. In effect, the outwardly directed extensions funnel the tip of a misaligned incoming male member toward the opening between the inwardly directed extensions of the female member, thereby aligning the male and female members.
In the disclosure which follows, the inwardly directed extensions of the female member will be referred to as xe2x80x9chooksxe2x80x9d whereas the outwardly directed extensions of the female member will be referred to as xe2x80x9cwingsxe2x80x9d.
Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.